Multiplex inertial filter, collector and separator

ABSTRACT

Methods and systems are provided for a multiplexed phase separating inertial filter that is composed of helical through holes generating centrifugal separating forces. In one example, the inertial filter may be a planar porous material with an array of helical channels, each helical channel of the array of helical channels extending from a top surface of the porous material to a bottom surface of the porous material.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to U.S. Provisional ApplicationNo. 63/262,803, entitled “MULTIPLEX INERTIAL FILTER, COLLECTOR ANDSEPARATOR,” and filed on Oct. 20, 2021. The entire contents of theabove-listed application are hereby incorporated by reference for allpurposes.

FIELD

The present description relates generally to liquid, gas, and/or solidphase separating filters.

BACKGROUND/SUMMARY

Numerous challenges are faced by the designers of life support systemsfor spacecraft because of the persistently unfamiliar and unforgivinglow-gravity (low-g) environment. A common challenge is the collection(filtration) of liquid droplets and solid particles from gas streams.Solid-gas and liquid-gas phase separations of dust, mists, sprays, etc.are pervasive and desired in numerous engineering systems (e.g.,liquid-gas sorbent chemistry, filtration, HVAC, demisters, firefightingequipment, and others). Such systems are often directly tied to lifesupport systems such as oxygen supply, air revitalization, thermalmanagement systems, water reclamation, medical fluids, etc. Priorsolutions include active separators and fine filters, both of whichpossess serious shortcomings of complexity and pressure drop. Activeseparators involve moving parts, which are disadvantageous due to addedpotential points of degradation that reduce reliability while increasingmass, power consumption, and noise. Fine filters also involvesignificant drawbacks that include high pressure drops due to thetortuous and low open area of such filters, as well as increasingpressure drop as saturation increases. Therefore, a porous media filtercapable of largely passive liquid droplet and particle collection andseparation is desired.

In order to at least partially address the issues described above, afilter described herein employs a deflected pathway, such as a helicalconduit geometry within a porous material, that exploits passivelyinduced centrifugal (inertial) forces on particle/liquid laden airflows.For example, particles/droplets are driven to conduit surfaces wherethey adhere and are wicked inward and thus collected in the porousmedia. The capillary wicking force leads to the uniform passivemigration of the fluid throughout the media for storage, furtherprocessing, or purge. The conduit pore dimension is expected to belarger than the media pore dimension. Thus, the variable porositycomponent (droplet phase separating media) exploits inertial, capillary,and wetting forces to quickly separate gas/vapor-driven droplet streamsinto single liquid and gas/vapor outlet flows in a short distance andwith low pressure drop. In one example, the media may include interwovenhelical through-holes in an otherwise porous capillary wicking media.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic of a filtration system incorporating aninertial filter.

FIG. 2 shows an example of a respirator incorporating an inertialfilter.

FIG. 3 shows a schematic example of an inertial filter with helicalthrough-holes.

FIG. 4 shows an example of a single helix channel configuration.

FIG. 5 shows an example of a double helix channel configuration.

FIG. 6 shows an example of a triple helix channel configuration.

FIG. 7 shows an array of triple helix channel configurations in anexploded view, a side view, and a cross-sectional view.

FIG. 8 shows a development of fluid flow through a curved path.

FIG. 9 shows a diagram of fluid flow through a porous material of aninertial filter.

FIG. 10 shows an exploded view, an angled view, a top view, and a sideview of a three-dimensional (3D) printed inertial filter with a filterhousing that includes a top plate and a bottom plate.

FIG. 11 shows an exploded view of a layered filter with the filterhousing.

FIG. 12 shows an example assembly of an inertial filter with drainingcapabilities.

FIGS. 4-7 and 10-12 are shown approximately to scale.

DETAILED DESCRIPTION

The following description relates to systems and methods for a multiplexphase separating inertial filter. The inertial filter may be included ina variety of applications, such as the carbon dioxide (CO₂) filteringsystem shown in FIG. 1 or the respirator shown in FIG. 2 . An example ofthe inertial filter that shows helical channels and a porous material isillustrated in FIG. 3. The inertial filter may have helical channelsthat may be configured in as a single helix, shown in FIG. 4 , a doublehelix, shown in FIG. 5 , or a triple helix, shown in FIG. 6 . The triplehelix configuration of FIG. 6 is further exemplified in FIG. 7 as anarray of triple helices. FIG. 8 schematically demonstrates how liquid iscaptured by the filter and gas flows through the filter. A furtherexample of the liquid capture process through porous material isdemonstrated in FIG. 9 . FIGS. 10 and 11 show a 3D printed filter (e.g.,a 3D printed monolith) and a layered filter made of laminate absorbentmaterial sheets, respectively, which may be included in a housing.Additionally, in some examples, the inertial filter may also be drainedof liquid to be continuously used without replacement. Therefore, anassembly allowing drainage is shown in FIG. 12 .

Turning now to the figures, a filtering system 100 is shown in FIG. 1 .The filtering system 100 includes an inertial filter 112. For example,the filtering system 100 may be used to filter carbon dioxide (CO₂) fromair within a closed system such as a space station. Furthermore, thefiltering system 100 advantageously uses the low pressure drop caused byhelical channels and wicking properties of the inertial filter 112 tofunction in the low pressure and gravity environments of space.

The filtering system 100 includes a pre-filter 104 through which air mayinitially enter and may be filtered of particulates, as shown by thedirection of an air flow arrow 102. A spray nozzle 106 is locateddownstream of the pre-filter 104. The spray nozzle 106 may introducedroplets to capture CO₂ within the air flow. For example, the dropletmay be a liquid amine that absorbs CO₂, such as diglycolamine (DGA),ethanolamine (MEA), ionic liquid, etc. A high surface area of thedroplets may allow for rapid absorption of the CO₂. A droplet laden flow130, which includes the absorbed CO₂ in the liquid amines as well as theremaining air (e.g., oxygen) flows downstream of the spray nozzle 106 tothe inertial filter 112. The liquid of the droplet laden flow 130 may becaptured by the inertial filter 112 using an array of helical structuresthat utilizes centrifugal force to move the liquid to an absorbentmaterial in the inertial filter 112. The process of the inertial filter112 is further described with respect to FIGS. 3 and 9 . Draining vias(not shown in FIG. 1 ) may transport the liquid from the inertial filterand flow from the inertial filter into a drain 114. The liquid may flowfrom the drain 114 through a first pipe 116 to a control valve 134(e.g., bypass valve) which controls the amount of liquid that isrecirculated and the amount of liquid that is processed at CO₂ processor132, which processes the CO₂ out of the liquid. The liquid that may beprocessed travels from the control valve 134, through a pipe 136 to theCO₂ processor 132. The liquid that has been processed at 132, which islean of CO₂, traverses through a pipe 138 to a pump 118 where the liquidthat is lean of CO₂ and liquid that has been recirculated by the controlvalve 134 through a pipe 117 to the pump 118 may both be pumped througha pipe 120 to the spray nozzle 106.

Gases, such as oxygen and nitrogen, may flow through the inertial filter112 and may continue to a fan 124, which may create the flow of airthrough the filtering system 100. The gases may then go through a highefficiency particulate air (HEPA) filter 126 to remove particulates suchas dust, pollen, mold, bacteria, etc. from the air flowing through theHEPA filter 126. As a result, an air flow 128 may be droplet free andhave decreased amount of particulates and CO₂.

Turning now to FIG. 2 , an example schematic of a respirator 200 with aninertial filter 208 is shown. For example, the respirator 200 may beused in space-based firefighting where the water droplets used to fightthe fire are filtered out of the airstream entering the respirator. Thisprevents the water droplets from obstructing the respirator. By usingthe inertial filter 208, airflow can continue unobstructed, with lowpressure drop, preventing droplet-induced blockage. Additionally,moisture inhalation may be reduced.

A user 202 may wear the respirator 200 with a face attachment 204covering the mouth and nose of the user 202. A direction of an air flow(which may include liquid droplets) entering the respirator 200 isindicated by arrows 210. The air may flow into the inertial filter 208,and the liquid droplets may be filtered out of the air flow by helicalpatterns within the inertial filter 208, leaving the remaining air to bedroplet-free. The droplet-free air may then enter a secondary filter206. For example, the secondary filter 206 may be a particulate filtercapable of capturing soot from a fire or other particulates that mayincrease a difficulty of breathing. The filtered air may then travelfrom the secondary filter through air passage ways 212 to enter the faceattachment 204 for the user 202 to breathe in.

Turning now to FIG. 3 , a perspective view of a section of a planarinertial filter 300 is shown. For example, the planar inertial filter300 may be the inertial filter 112 within the filtering system 100 shownin FIG. 1 or the inertial filter 208 that is a part of the respirator200 shown in FIG. 2 . In some examples, the planar inertial filter 300may be shaped as a cone, sphere, etc. The planar inertial filter 300includes a plurality of helical through-channels 310 within a porousmaterial 306 and with a plurality of entrance holes 304. Dimensions(e.g., length, width, diameter, etc.) of the plurality of helicalthrough-channels 310 are larger than dimensions of pores of the porousmaterial 306. As a result, the planar inertial filter 300 exploitsinertial, capillary, and wetting forces to separate the gas, liquid orparticles entering the planar inertial filter 300. The plurality ofhelical through-channels 310 are shown as a single helix, however, inother examples, the plurality of helical through-channels 310 may beconfigured as double or triple helices, as further elaborated withrespect to FIGS. 4-6 . The planar inertial filter 300 may be used toperform liquid-gas, solid-gas, and solid-liquid-gas phase separationsfor droplets/particles of a wide range of length-scales includingcentimeter to micrometer sizes. The planar inertial filter 300additionally contains no moving parts, low pressure losses, a constantpressure drop, and no additional power consumption due to its passiveseparation method utilizing motive fluid streams. This may increase areliability of the planar inertial filter 300.

A liquid/gas mixture 312, which may be a mixture of gas, liquiddroplets, and/or particulates of a variety of diameters and diameterdistributions may flow into the planar inertial filter 300 as indicatedby an air flow arrow 302. For example, the air flow may be drivenexternally by a blower, fan, buoyancy, gravity, etc. The liquid/gasmixture 312 may enter through the plurality of entrance holes 304 andflow through the plurality of helical through-channels 310. Centrifugalaccelerations drive the liquid of the liquid/gas mixture 312 to theouter walls of the plurality of helical through-channels 310 wheredroplets may impinge onto the porous material 306, which absorbs and mayretain the droplets from the liquid/gas mixture 312. For example, thedroplets and/or particles may spread and distribute within the porousmaterial 306 by capillary forces, directing the droplets and/orparticles away from the plurality of helical through-channels 310, whichremain open to the gaseous air flow. A length and diameter of theplurality of helical through-channels 310 include a margin fordeveloping flows, local recirculation, droplet rolling, and satellitedroplet rebound. The length, diameter, and number of helical channels isselected to remain below pressure drop specifications. Although notshown in FIG. 3 , the porous material 306 may incorporate drain vias, anexample of which is shown in FIG. 12 and described below. In situationsof high gravity (e.g., the surface gravity of the Earth), liquid withinthe porous material 306 may drain via gravity. In situations of lowgravity (e.g., in space), the liquid within the porous material 306 maydrain out of the porous material 306 through the drain vias, asindicated by the liquid drain arrow 314. In other examples, the impingedliquids and/or particulates may be stored within the porous material306. As a further example, filtration through the planar inertial filter300 may continue until the porous material 306 is saturated. In someexamples, when the porous material is saturated, the inertial filter maybe replaced. In other examples, such as the inertial filter 218 of FIG.1 , the inertial filter may be drained for continuous use. Gases fromthe air traveling through the plurality of helical through-channels 310may exit the planar inertial filter 300 as indicated by a gas exit arrow316. For example, the gas that exits may be free from liquid dropletsand/or particles.

Continuing now to FIG. 4 , a single helix configuration 400 comprisingone helical passage is shown in a perspective view 402 and in a sideview 404. For example, the single helix configuration 400 may beimplemented within the inertial filter 112 shown in FIG. 1 or theinertial filter 208 shown in FIG. 2 . As a further example, the singlehelix configuration 400 is shown in FIG. 3 . Reference axes 499 areincluded in both the perspective view 402 and side view 404 in order tocompare the views and relative orientations described below. Referenceaxes 499 includes three axes, namely an x-axis, a y-axis, and a z-axis.A positive direction for each axis is indicated by an arrow. Thepositive direction of the y-axis points out of the page in the side view404 as shown by a circle.

The single helix configuration 400 includes a helical passage 406 withina porous material 450. The helical passage 406 includes an entrance hole408, an exit hole 410, and a pitch 418 (e.g., a height of one full helixturn, measured parallel to a central axis 490). The helical passage 406includes the central axis 490, which is shown in the side view 404 andis parallel to the z-axis. In the example shown in FIG. 4 , the helicalpassage 406 maintains an equal radial distance from the central axis 490(e.g., a distance from the central axis parallel to an x-y plane of thereference axes 499). In other examples, the radial distance between thecentral axis 490 and the helical passage 406 may fluctuate about thecentral axis 490. For example, the radial distance for each turn may bedifferent, or, as another example, the radial distance may be similarfor some turns and different for others. As a further example, theradial distance may alternate between two or more different radii.

Additionally, the helical passage 406 is shown completing one and a halfrotations where a rotation is a 360 degree turn; however, any number ofrotations may be used. For example, the helical passage 406 may complete1, 2, 3, or more rotations and the rotations may be full or partial(e.g., 0.25, 0.50, 0.75, etc.). More rotations or fewer rotations may beadded or removed by changing the pitch 418 or by increasing a length thehelical passage 406 within the porous material 450.

Furthermore, the helical passage 406 extends from the entrance hole 408at a top surface 489 of the porous material 450 to the exit hole 410 ata bottom surface 488 of the porous material 450, forming a tubular voidin the porous material 450. For example, the entrance hole 408 is afirst opening defined by a circular edge on the top surface 489 meetinginternal walls of the helical passage 406 and may not be obstructed withthe porous material 450. Similarly, the exit hole 410 is a secondopening defined by a circular edge on the bottom surface 488 meetinginternal walls 482 of the helical passage 406 and may not be obstructedwith the porous material 450. The helical passage 406 may be a fluidicpassage with internal walls 482 passing through the porous material 450,but distinct from interstitial spaces of the porous material 450. Theinternal walls 482 are open to the porous material 450 via the porosityof the porous material 450. For example, the helical passage 406 is nota passage formed by the general porosity of the porous material 450.

In some embodiments, an entrance diameter 412 of the entrance hole 408may be equal to a channel diameter 416 of the helical passage 406 and/orequal to an exit diameter 414 of the exit hole 410. As another example,the channel diameter 416 may be smaller than the entrance diameter 412and the exit diameter 414 (e.g., the channel diameter 416 may taper outnear the exit hole 410 and entrance hole 408).

A combination of liquids, gases, and/or solids may enter the helicalpassage 406, which may be a tubular void within the porous material,through the entrance hole 408. As the liquid, gases, and/or solids passthrough the helical passage 406 the liquids and/or solids may impinge onand be absorbed and retained by the porous material 450. As such,liquids and/or solids may not exit through the exit hole 410, leavinggases to exit the helical passage 406 through the exit hole 410.

Turning now to FIG. 5 , a double helix configuration 500 comprising twohelical passages is shown in a perspective view 502 and in a side view504. For example, the double helix configuration 500 may be implementedwithin the inertial filter 112 shown in FIG. 1 or the inertial filter208 shown in FIG. 2 . As a further example, the double helixconfiguration 500 may be used in an inertial filter in combination withthe single helix configuration 400 of FIG. 4 . For example, there may bealternating rows of the single helix configuration 400 and the doublehelix configuration 500, or, as another example, the single helixconfiguration 400 and the double helix configuration 500 may alternateone after the other such that similar configurations are not directlynext to each other. Additionally, the double helix configuration 500 maybe selected where increased flow per volume is desired instead ofadditional porous material to hold filtered liquids and/or solids.Reference axes 599 are included in both the perspective view 502 andside view 504 in order to compare the views and relative orientationsdescribed below. Reference axes 599 includes three axes, namely anx-axis, a y-axis, and a z-axis. A positive direction for each axis isindicated by an arrow. The positive direction of the y-axis points outof the page in the side view 504 as shown by a circle.

The double helix configuration 500 includes a first helical passage 506with a first entrance hole 508, a first exit hole 510, and first pitch518. The double helix configuration 500 additionally includes a secondhelical passage 526 with a second entrance hole 528, a second exit hole530, and a second pitch 538. The first helical passage 506 and secondhelical passage 526 are shown twisting around a central axis 590, whichis shown on the side view 504 and is parallel to the z-axis. As shown inthe double helix configuration 500, the first helical passage 506 andthe second helical passage 526 may maintain an equal radial distanceaway from the central axis 490. In other examples, the first helicalpassage 506 and/or the second helical passage 526 may fluctuate a radialdistance away from the central axis 590 (e.g., a distance from thecentral axis parallel to an x-y plane of the reference axes 599). Forexample, the radial distance for each turn may be different, or, asanother example, the radial distance may be similar for some turns anddifferent for others. As a further example, the radial distance mayalternate between two or more different radii.

Additionally, the first helical passage 506 and the second helicalpassage 526 are shown completing one and a half rotations where arotation is a 360 degree turn, however, any number of rotations may beused. For example, the first helical passage 506 and the second helicalpassage 526 may complete 1, 2, 3, or more rotations, and the rotationsmay be complete or partial (e.g., 0.25, 0.50, 0.75, etc.). Morerotations or less rotations may be added or removed by changing thefirst pitch 518 and the second pitch 538 and/or by increasing a lengthof the first helical passage 506 and the second helical passage 526 takeup within a porous material 550.

Furthermore, the first helical passage 506 and the second helicalpassage 526 may extend from a top surface 589 of the porous material 550to a bottom surface 588 of the porous material 550. For example, thefirst entrance hole 508 and second entrance hole 528 may be firstopenings defined by a circular edge located on the top surface 589 andmay not be obstructed with the porous material 550. Similarly, the firstexit hole 510 and second exit hole 530 may be second openings defined bya circular edge located on the bottom surface 588 and may not beobstructed with the porous material 550. The first helical passage 506and the second helical passage 526 may be fluidic passages with internalwalls 582 and internal walls 584, respectively, passing through theporous material 550 but are distinct from interstitial spaces of theporous material 550. The internal walls 582 and internal walls 584 areopen to the porous material 550 via the porosity of the porous material550. For example, the first helical passage 506 and the second helicalpassage 526 are not passages formed by the general porosity of theporous material 550.

A first entrance diameter 512 of the first entrance hole 508 may beequal to a first channel diameter 516 of the first helical passage 506and/or equal to a first exit diameter 514 of the first exit hole 510. Asanother example, the first channel diameter 516 may be smaller than thefirst entrance diameter 512 and the first exit diameter 514 (e.g., thefirst channel diameter 516 may taper out near the first exit hole 510and the first entrance hole 508). A second entrance diameter 529 of thesecond entrance hole 528 may be equal to a second channel diameter 536of the second helical passage 526 and/or equal to a second exit diameter534 of the second exit hole 530. As another example, the second channeldiameter 536 may be smaller than the second entrance diameter 529 andthe second exit diameter 534. As a further example, some, all, or noneof the first entrance diameter 512, first channel diameter 516, andfirst exit diameter 514, the second entrance diameter 519, secondchannel diameter 536, and second exit diameter 534 may be equal to eachother.

As an additional example, the first pitch 518 and the second pitch 538may be equal and sized such that the first helical passage 506 and thesecond helical passage 526 do not intersect. In this way, flow throughthe inertial filter may be increased for a given packing density. Insituations of low gravity (e.g., in a space station), small volume itemsare desired. The double helix configuration 500 decreases an amount oflinear space used for filtering, making it a desirable configuration forlow gravity environments.

A combination of liquids, gases, and/or solids may enter the firsthelical passage 506 and the second helical passage 526, which both maybe a void within the porous material, through the first entrance hole508 and the second entrance hole 528 respectively. As the liquids,gases, and/or solids pass through the first helical passage 506 and thesecond helical passage 526, the liquids and/or solids may impinge on andbe absorbed by the porous material 550. As such, liquids and/or solidsmay not exit through the first exit hole 510 nor the second exit hole530, leaving gases to exit the first helical passage 506 through thefirst exit hole 510 and to leave the second helical passage 526 throughthe second exit hole 530.

Turning now to FIG. 6 , a triple helix configuration 600 comprisingthree helical passages is shown in a perspective view 602 and in a sideview 604. For example, the triple helix configuration 600 may beimplemented within the inertial filter 112 shown in FIG. 1 or theinertial filter 208 shown in FIG. 2 . As a further example, the triplehelix configuration 600 may be used in an inertial filter in combinationwith the single helix configuration 400 of FIG. 4 and/or the doublehelix configuration 500 of FIG. 5 . For example, there may bealternating rows of the single helix configuration 400, the double helixconfiguration 500, and/or the triple helix configuration 600, or, asanother example, the single helix configuration 400, the double helixconfiguration 500, and/or the triple helix configuration 600 mayalternate one after the other. Additionally, the triple helixconfiguration 600 may be preferred over the double helix configuration500 and the single helix configuration 400 where increased flow pervolume instead of additional porous material to hold filtered liquidsand/or solids is desired. Reference axes 699 are included in both theperspective view 602 and side view 604 in order to compare the views andrelative orientations described below. Reference axes 699 includes threeaxes, namely an x-axis, a y-axis, and a z-axis. A positive direction foreach axis is indicated by an arrow. The positive direction of the y-axispoints out of the page in the side view 604 as shown by a circle.

The triple helix configuration 600 includes a first helical passage 606with a first entrance hole 608, a first exit hole 610, and first pitch618. The triple helix configuration 600 additionally includes a secondhelical passage 626 with a second entrance hole 628, a second exit hole630, and a second pitch 638. Furthermore, a third helical passage 660with a third entrance hole 668, a third exit hole 670, and a third pitch678 is included within the triple helix configuration 600. The firsthelical passage 606, second helical passage 626, and third helicalpassage 660 are shown twisting around a central axis 690, which is shownon the side view 604 and is parallel to the z-axis. As shown in thetriple helix configuration 600, the first helical passage 606, thesecond helical passage 626, and third helical passage 660 may maintainan equal radial distance away from the central axis 590. In otherexamples, the first helical passage 606, the second helical passage 626,or the third helical passage 660 may fluctuate a radial distance awayfrom the central axis 690 (e.g., a distance from the central axisparallel to an x-y plane of the reference axes 699). For example, theradial distance for each turn may be different, or, as another example,the radial distance may be similar for some turns and different forothers. As a further example, the radial distance may alternate betweentwo or more different radii. Additionally, the first helical passage606, second helical passage 626, and third helical passage 660 are showncompleting one and a half rotations where a rotation is a 360 degreeturn, however, any number of rotations may be used. For example, 1, 2,3, or more rotations may be completed, and the rotations may be completeor partial (e.g., 0.25, 0.50, 0.75, etc.).

Furthermore, the first helical passage 606, the second helical passage626, and the third helical passage 660 extend from a top surface 689 ofthe porous material 650 to a bottom surface 688 of the porous material650. For example, the first entrance hole 608, the second entrance hole628, and the third entrance hole 668 may be openings defined by acircular edge located on the top surface 689 and may not be obstructedwith the porous material 650. Similarly, the first exit hole 610, thesecond exit hole 630, and the third exit hole 670 may be defined by acircular edge located on the bottom surface 688 and may not beobstructed with the porous material 650. The first helical passage 606includes internal walls 682, the second helical passage 626 includesinternal walls 684, and the third helical passage 660 includes internalwalls 686. The internal walls 682, internal walls 684, and internalwalls 686 may be open to the porous material 650 via the porosity of theporous material 650. For example, the first helical passage 606, thesecond helical passage 626, and the third helical passage 660 are notpassages formed by the general porosity of the porous material 650.

A first entrance diameter 612 of the first entrance hole 608 may beequal to a first channel diameter 616 of the first helical passage 606and/or equal to a first exit diameter 614 of the first exit hole 610. Asanother example, the first channel diameter 616 may be smaller than thefirst entrance diameter 612 and the first exit diameter 614. A secondentrance diameter 629 of the second entrance hole 628 may be equal to asecond channel diameter 636 of the second helical passage 626 and/orequal to a second exit diameter 634 of the second exit hole 630. Asanother example, the second channel diameter 636 may be smaller than thesecond entrance diameter 629 and the second exit diameter 634. A thirdentrance diameter 672 of the third entrance hole 668 may be equal to athird channel diameter 676 of the third helical passage 660 and/or equalto a third exit diameter 674 of the third exit hole 670. As anotherexample, the third channel diameter 676 may be smaller than the thirdentrance diameter 672 and the third exit diameter 674. As a furtherexample, all, some or none of the third entrance diameter 672, the thirdchannel diameter 676, and the third exit diameter 674, the firstentrance diameter 612, first channel diameter 616, and first exitdiameter 614, and the second entrance diameter 619, second channeldiameter 636, and second exit diameter 634 may be equal.

As an additional example, the first pitch 618, the second pitch 638, andthe third pitch 678 may be equal such that the first helical passage606, the second helical passage 626, and the third helical passage 660do not intersect. In this way, flow through the inertial filter may beincreased for a given packing density. In situations of low small volumeitems are desired (e.g., in a space station), the triple helixconfiguration 600 decreases an amount of linear space desired forfiltering while increasing a flow through the inertial filter, which mayincrease an amount filtered for a given time period.

A combination of liquid, gases, and/or solids may enter the firsthelical passage 606 through the first entrance hole 608, enter thesecond helical passage 626 through the second entrance hole 628, andenter the third helical passage 660 through the third entrance hole 668.As the liquid, gases, and/or solids pass through the first helicalpassage 606, the second helical passage 626, and the third helicalpassage 660 the liquids and/or solids may impinge on and be absorbed bythe porous material 650. As such, liquids and/or solids may not exitthrough the first exit hole 610, the second exit hole 630, nor the thirdexit hole 670, leaving gases to exit the first helical passage 606through the first exit hole 610, exit the second helical passage 626through the second exit hole 630, and exit the third helical passage 660through the third exit hole 670.

FIG. 7 shows an array 700 of a plurality of helical passage units 720(e.g., helical passages that may be in a single, double, or triple helixconfiguration) that may be within a planar inertial filter. The array700 is shown in an exploded view 701, a side view 702, and across-sectional view 704. The exploded view 701 shows a first 3D volume706, a first cross-section 708, a second cross-section 710, and a second3D volume 712. The array 700 may be a section of the inertial filter 112of the filtering system 100 shown in FIG. 1 or a section of the inertialfilter 208 shown in FIG. 2 . Reference axes 799 are included in allviews in order to compare the views and relative orientations describedbelow. Reference axes 799 includes three axes, namely an x-axis, ay-axis, and a z-axis. A positive direction for each axis is indicated byan arrow. The positive direction of the y-axis points out of the page inside view 702 as shown by as the circle, and the positive direction ofthe z-axis points out of the page in the cross-sectional view 704.

The helical passage units 720 are shown within a planar porous material750 and are examples of the triple helix configuration 600 shown in FIG.6 . In other examples, the array 700 of helical passage units 720 may bethe single helix configuration 400 shown in FIG. 4 , the double helixconfiguration 500 shown in FIG. 5 , or a mixture of two or more of thehelix configurations. The array 700 is shown as one row with fivehelical passage units 720 and 15 (e.g., five sets of triple helicalconfigurations) helical passage units 720, however, within the inertialfilter, there may be a plurality of rows with more or fewer helicalpassage units 720. For an example, an inertial filter may include anamount of rows between 1 to 5, 5 to 10, 15 to 20, 20 to 50, or more. Thehelical passage units may be arranged in an array with equal dimensionswithin the inertial filter to form a square filter or may have unequaldimensions to form a rectangular filter. In other examples, the helicalpassage units 720 may be arranged in a circle, spiral, or oblong shapeto fit packaging desires for the inertial filter. The amount of helicalpassage units 720 within an inertial filter may depend on the amount ofrows and the helical configuration (e.g., packing density) of thehelical passage units 720. Additionally, the helical passage units 720may be interwoven or overlapped in tighter arrays to increase mediaporosity. As a further example, the helical passage units 720 mayalternate from right handed thread and left handed thread for net flowuniformity.

The side view 702 includes a cross-sectional line 714 parallel to thex-axis to show where the cross-sectional view 704 originates in thearray 700 of the helical passage units 720. Furthermore, in the sideview 702, a pitch 716 parallel to the z-axis is shown. In the example ofthe array 700, the helical channels all have an equal pitch 716,however, in other examples, the helical channels may have unequalpitches. The pitch 716 is shown as an example of a smaller pitch than isshown in FIGS. 4, 5, and 6 , and as a result, the helical passage units720 are more tightly packed, but still not overlapping. In this way, theflow through a packing density of the inertial filter may be increased.

The cross-sectional view 704 shows the horizontal cross sections of atriple helix (e.g., three non-touching kidney shaped holes) from thecross-sectional line 714. A length 718 of one helical channel is shown.In the example array 700, the length 718 may be equal for all thehelical channels. In other examples, such as when a pitch of the helicalchannels is unequal or a radial distance from a center axis is unequalthe length 718 may not be equal for all helical channels. As anotherexample, the length 718 may increase with a smaller pitch or decreasewith a larger pitch.

Turning now to FIG. 8 , the development of fluid flow around a curvedpath 800 is shown. The curved path 800 may be a section of a helicalpath (e.g., helical passage). The development of fluid flow includesliquid drift, impact (e.g., impingement), and capillary absorption. Thefluid flow development around the curved path 800 is an example of thedevelopment of fluid flow within an inertial filter with helicalchannels. As a further example, the fluid flow development of the curvedpath 800 may be included in the inertial filter 112 of FIG. 1 and theinertial filter 208 of FIG. 2 . The fluid flow is shown in differentsections throughout the curved path 800. For example, the fluid flowincludes a first section that is a disperse flow section 804, a secondsection that is a partially developed annular flow section 806, a thirdsection that is a partially developed asymmetric annular flow section808, a fourth section that is a more fully developed annular flowsection 810, and a fifth section that is fully developed annular flowwith fully caught liquid section 812. Although only the above-mentionedsections are explicitly illustrated, it may be understood thatdevelopment of fluid flow acts in a similar way at the boundary of eachillustrated section and/or may be transitioning between two differentsections proximate to each other. For example, between the partiallydeveloped asymmetric annular flow section 808 and the fully developedannular flow section 810, which are proximate to each other, the fluidflow may be continuously or abruptly changing from, as an example, thepartially developed asymmetric annular flow to fully developed annularflow. Further, the annular flow film thickness may be regulated by theliquid wicking rate into the porous media.

A liquid/gas mixture 802 enters the curved path 800 at an entrance 838.The liquid/gas mixture 802 may be a combination of gas and liquid. Forexample, the air may be a 90:10 ratio of gas to liquid, or, in otherexamples, the ratio of gas to liquid may be 85:15, 95:5, or 99:1. As theliquid/gas mixture 802 enters, the fluid flow is that of the disperseflow section 804. The fluid flow may continue farther in a directionshown by direction arrows 816 through the curved path 800.

At the partially developed annular flow section 806, centrifugal forceswithin the curved path 800 cause liquids within the liquid/gas mixture802 to impinge on an outer wall 830 and an inner wall 832, as shown byouter impingement arrows 836 and inner impingement arrows 834. As theliquid impinges on the outer wall 830 and inner wall 832, the liquid isabsorbed by a porous material 850. Through capillary action, the porousmaterial may flow the absorbed liquid away from the curved path 800 toallow further capture of liquid. Due to liquid within the liquid/gasmixture 802 being absorbed by the porous material 850, the ratio of gasto liquid may increase. The liquid/gas mixture 802 may then continuefarther through the curved path 800 as shown by the direction arrows 816and reach the partially developed somewhat asymmetric annular flowsection 808. Once fluid has developed to the partially developedasymmetric annular flow section 808, more liquid may impinge on theouter wall 830 than the inner wall 832, as shown by the decreased amountof inner impingement arrows 834 and increased outer impingement arrows836.

The ratio of gas to liquid of the liquid/gas mixture 802 may furtherincrease as more liquid is being absorbed within the partially developedasymmetric annular flow section 808 and at a transitionary area betweenthe partially developed asymmetric annular flow section 808 and thefully developed annular flow section 810. Liquid within the fullydeveloped annular flow section 810 may be impinging mostly or fully onthe outer wall 830 as shown by the outer impingement arrows 836. Theimpinging liquid gets caught and absorbed by the porous material 850such that the ratio of gas to air is further increased. The liquid/gasmixture 802 continues through the curved path 800, with liquidcontinuing to be absorbed, reaching the fully developed annular flowwith fully caught liquid section 812, at which section the fluid flow isfully developed annular flow, similar to the fully developed annularflow section 810, however, the liquid in the fully developed annularflow with fully caught liquid section 812 is almost fully or is fullycaptured and absorbed in the porous material. In this way, an exitingair 814 may be approximately 100% gas.

Referring now to FIG. 9 , a section of an inertial filter 900 showsmovement of liquid through a helical channel 910 and a planar porousmaterial 904. For example, the helical channel 910 may be any of thehelical channel examples shown in FIGS. 4-6 . The inertial filter 900may be a part of the inertial filter 112 shown in FIG. 1 and/or theinertial filter 208 shown in FIG. 2 . Reference axes 999 includes threeaxes, namely an x-axis, a y-axis, and a z-axis. A positive direction foreach axis is indicated by an arrow. The positive direction of the x-axispoints out of as shown by a circle.

Liquid droplets 902 may enter the helical channel 910, which is atubular void extending from a top surface of the planar porous material904 to a bottom surface of the planar porous material 904, and be drivento outer surfaces 912 where the liquid droplets impact, adhere, and arewicked into the planar porous material 904 parallel to the y-axis at aknown rate based on the fluid properties, pore size and droplet flowrate. The liquid droplets 902 may then spread to the surrounding planarporous material 904 through capillary action in the direction of fluidflow arrows 906. As a result of the liquid moving through the porousmaterial away from the helical channel 910, room is made for incomingliquid droplets 902. By using the helical channel design and liquidwicking properties of the planar porous material 904, the helicalpassageways remain open to the gas flow such that there remains a lowpressure drop throughout the inertial filter 900, which works forfiltering in environments where low volume and low pressure drop isdesired, such as in low-gravity environments aboard spacecraft. Forexample, the filter pressure drop remains constant until the planarporous material 904 is fully saturated. If the planar porous material904 is fully saturated, the liquid may be blown out, for example, via anair flow introduced into the planar porous material 904, to a draininglocation (e.g., at a back side of the inertial filter 900). Drainingvias, which are shown in FIG. 10 and explained in greater detail below,may be added to operate in a steady drain mode resulting in the pressuredrop to remain constant provided the droplet capture rate does notexceed the liquid drain rate from the draining vias.

FIG. 10 shows an exploded view 1000, an angled view 1002, a top view1004, and a side view 1006 of a filter assembly 1099. The filterassembly 1099 comprises a 3D printed (3DP) filter 1010 made of absorbentmaterial and helical channels 1016, a top plate 1008, and a bottom plate1012. The top plate 1008 and the bottom plate 1012 may herein bereferred to as a filter housing when combined to hold the 3DP filter1010, as shown in the angled view 1002, the top view 1004, and the sideview 1006. For example, the filter housing and the 3DP filter 1010 maybe implemented in the filtering system 100 shown in FIG. 1 . The filterhousing may hold the 3DP filter 1010 in place so that movement of thefilter is decreased. For example, the 3DP filter 1010 may be containedwithin the filter housing.

Reference axes 1098 are included in all views in order to compare theviews and relative orientations described below. Reference axes 1098includes three axes, namely an x-axis, a y-axis, and a z-axis. Apositive direction for each axis is indicated by an arrow. The positivedirection of the z-axis points out of the page in the top view 1004 asshown by as the circle, and the positive direction of the x-axis pointsout of the page in the side view 1006.

The top plate 1008 is shaped as a square or rectangle and has a length1031 parallel to the y-axis and a width 1033 parallel to the x-axis. Thelength 1031 may be equal to, greater than, or smaller than the width1033. In the example shown in FIG. 10 , the length 1031 and the width1033 are equal, creating a square shape. Indents on each side of the topplate 1008 are included such that each of the four corners protrudecompared to the sides. An indentation length 1030 (e.g., a length of theindentation parallel to the length 1031) is shown in the exploded view1000 along with an indentation width 1032 (e.g., a length of theindentation parallel to the width 1033). The indentation length 1030 issmaller than the length 1031, and the indentation width 1032 is smallerthan the width 1033. In some examples, the indentation length 1030 maybe equal to the indentation width 1032. In other examples, such as whenthe length 1031 and the width 1033 are not equal, the indentation length1030 may not be equal to the indentation width 1032. The top plate 1008also contains a lattice structure 1014 with some lattices parallel tothe y-axis and some parallel to the x-axis which may be able to hold thefilter in place while not blocking entrances and/or exits (e.g., the topplate 1008 may be in contact with either the entrances or the exits) tothe helical channels 1016 (e.g., helical passages) on the 3DP filter1010.

The helical channels 1016 are shown arranged in a porous material 1050in an array with rows of alternating amounts of triple helixconfigurations (e.g., the triple helix configuration 600 shown in FIG. 6) on the 3DP filter 1010. For example, a first row shows 6 of the triplehelix configurations, while a second row shows 7 triple helixconfigurations, repeating this pattern 3.5 more times. In otherexamples, each row may contain equal amounts of helical channels 1016.In other examples still, the helical channels 1016 may not be arrangedin rows and instead in concentric circles, spirals, etc. Furthermore,the helical channels 1016 may instead be configured as a single helix(e.g., the single helix configuration 400 shown in FIG. 4 ), as doublehelices (e.g., the double helix configuration 500 shown in FIG. 5 ), acombination of the three configurations, or other overlapping,interwoven, or counter rotating configurations. In some embodiments,different configurations of helices may be combined in the 3DP filter1010. For example, a first portion of the 3DP filter 1010 (e.g., at acenter of the 3DP filter 1010) may include helices in a firstconfiguration, a second portion of the 3DP filter 1010 (e.g., at aperiphery of the 3DP filter 1010) may include helices in a secondconfiguration, and so on.

The 3DP filter 1010 may exhibit a multi-scale porosity: a large-scalehelical pore (e.g., the helical channels 1016) for low-resistance airflow and a small-scale pore (e.g., the porous material 1050) for wettingand holding of separated liquid droplets. In some embodiments, theporosity of the porous material 1050 may vary across the 3DP filter1010. For example, a first portion of the porous material 1050 mayinclude a first small-scale pore, a second portion of the porousmaterial 1050 may include a second small-scale pore, and so on.

The 3DP filter 1010 may be printed of any variety of metallic,polymeric, or other synthetic or natural material. Material selectionmay be made broadly on filter objectives, performance requirements, andmaterial compatibility. Poorly wetting materials may be accommodated byprocedure; such as by prewetting/saturating the media with the testliquid before operation. As described in greater detail below, the 3DPfilter may also be printed with an open cavity within which incrementedlayers (stacks) of perforated porous metallic, polymeric, or othersynthetic or natural material fabric sheets are laid creating theparallel helical passageways described herein.

The bottom plate 1012 has a length 1046 parallel to the y-axis and awidth 1048 parallel to the x-axis. The length 1046 may be equal to thelength 1031 of the top plate 1008 and the width 1048 may be equal to thewidth 1033 of the top plate such that when the top plate 1008 and thebottom plate 1012 are in contact with each other (as shown in the angledview 1002, the top view 1004, and the side view 1006) the top plate 1008does not extend past the bottom plate 1012 nor does the top plate 1008fit inside the bottom plate 1012. The bottom plate 1012 has a height1052 parallel to the z-axis, which may be sized to accommodate a height1054 of the 3DP filter 1010 within the bottom plate 1012. A length 1036of the 3DP filter 1010 may be smaller than the length 1046 of the bottomplate 1012, and a width 1034 of the 3DP filter 1010 may be smaller thanthe width 1048. However, an interior length 1040 of the bottom plate1012 may be equal to the length 1036 of the 3DP filter 1010 along withan interior width 1038 of the bottom plate 1012 may be equal to thewidth 1034 of the 3DP filter 1010. As such, the 3DP filter 1010 may fitwithin the bottom plate 1012 with sides 3DP filter 1010 touchinginterior walls of the bottom plate 1012, which may promote stability anddecrease movement of the 3DP filter 1010. The differences between thelength 1046 and interior length 1040 is attributed to a thickness 1056of the housing. The thickness 1056 accounts also for the differencesbetween the width 1048 and interior width 1038. The bottom plate 1012also includes a lattice structure 1020 at an opposite end of the topplate 1008, which may be able to hold the filter in place while notblocking entrances and/or exits (e.g., the bottom plate 1012 may be incontact with either the entrances or the exits) to helical channels 1016on the 3DP filter 1010.

A top surface 1060 of the bottom plate 1012 contain protrusions 1058.Protrusions 1058 parallel to the length 1046 of the bottom plate 1012may have a length 1042 which is equal to the indentation length 1030 ofthe top plate 1008. Additionally, protrusions parallel to the width 1048have a width 1044 which is equal to the indentation width 1032 of thetop plate 1008. As such the protrusions 1058 of the bottom plate 1012may fit within the indentations of the top plate 1008 (shown in theangled view 1002, top view 1004, and side view 1006) using friction tocouple the bottom plate 1012 and the top plate 1008. Furthermore, thetop plate 1008 and the bottom plate 1012 may form a flush surface whencoupled. In this way the housing may hold the 3DP filter 1010 in place.

Continuing now to FIG. 11 , an exploded view 1100 of a filter assembly1199 is shown. The filter assembly 1199 includes the top plate 1008, alayered filter 1106, and the bottom plate 1012. The top plate 1008 andthe bottom plate 1012 are described above with respect to FIG. 10 andwill not be re-introduced. The layered filter 1106 may fit within thebottom plate 1012 in a similar way as described with the 3DP filter 1010shown in FIG. 10 . In this example, the layered filter 1106 is shown inan exploded view with a plurality of laminated sheets 1108 separate froma main mass 1110. Reference axes 1198 includes three axes, namely anx-axis, a y-axis, and a z-axis. A positive direction for each axis isindicated by an arrow.

The layered filter 1106 may be a stack layup of wetting paper/filtermedia that, once aligned, forms helical pores (e.g., helical channels1016) and provides a means to hold separated liquid via wicking andabsorption. The layered filter 1106 may be a thin material comprised of,for example, a combination of Rayon and polyester that is readilywettable by water. To create the helical pores on a lay of the layeredfilter 1106, laser cutting may be used. One advantage of using lasercutting is that it may not use upfront tooling and can adapt to anygeometry by simply changing a graphic file used for giving instructionsto the laser cutter (as opposed to producing a new tool). As anotherexample, a die punch for each layer may be created and combined togetherto make a single tool, decreasing filter production time.

Turning now to FIG. 12 , an example assembly 1200 of an inertial filteris shown in an angled view 1202 and an exploded view 1203. In someexamples of inertial filters, absorbent materials can be added to arigid 3DP filter structure to enhance draining. This creates a mechanismto continuously separate, filter, and drain liquids indefinitely. Alayered laminated version (not 3DP) can also be constructed by addingstructures or layers that promote directional draining. The assembly1200 includes a helix material 1204, drain connectors 1208, a parallelporous material 1212 (e.g., parallel to the drain connectors 1208) and aperpendicular porous material 1214 (e.g., perpendicular to the drainconnectors 1208), and draining vias 1218. The perpendicular porousmaterial 1214 may be the same as the parallel porous material 1212, orthe parallel porous material 1212 may be different from the parallelporous material 1212. The assembly 1200 may be used in the inertialfilter 112 shown in FIG. 1 . Reference axes 1299 includes three axes,namely an x-axis, a y-axis, and a z-axis. A positive direction for eachaxis is indicated by an arrow.

The helix material 1204 may have a flow of air, which may include gasesand liquids, through helical passages on the helix material 1204. Thehelix material may separate the liquid and gases in the air usingcentrifugal (e.g., inertial) forces to push the liquid to the sides ofthe helical passages and be absorbed by the parallel porous material1212. The drain connectors 1208 may be coupled to the helix material1204 on opposite sides (e.g., sides that are parallel to each other) ofthe helix material 1204. The drain connectors 1208 may be locatedparallel to the draining vias, which are used to transport liquid flowfrom the parallel porous material 1212 to the perpendicular porousmaterial 1214. The drain connectors 1208 may then collect and drainliquid from the perpendicular porous material 1214. As an example, asingle droplet of liquid may enter the helix material 1204 via a helicalpassage, and may be driven to impinge upon a portion of porous materialon an interior surface of the helical passage. The droplet may be drawnto a nearest draining via 1218 lined with the parallel porous material1212 (e.g., via capillary action). The droplet may then be drawn downthe parallel porous material 1212 lining the draining via 1218 untilreaching the perpendicular porous material 1214. Finally, the dropletmay be drawn towards a center of the perpendicular porous material 1214at a location of a drain connector 1208, where the liquid may be drainedout of the filter assembly 1200.

In this way, an inertial filter including helical passages within aporous material may perform liquid-gas, solid-gas, and solid-liquid-gasphase separations for droplets/particles of a wide range oflength-scales including centimeter to micrometer sizes. Furthermore, theinertial filter advantageously has no moving parts, low pressure losses,constant pressure drop, and no additional power consumption due to itspassive separation method utilizing motive fluid streams, geometric flowcomponents, and capillary (wicking) forces.

FIGS. 1, 4-7, and 10A-12 show example configurations with relativepositioning of the various components. If shown directly contacting eachother, or directly coupled, then such elements may be referred to asdirectly contacting or directly coupled, respectively, at least in oneexample. Similarly, elements shown contiguous or adjacent to one anothermay be contiguous or adjacent to each other, respectively, at least inone example. As an example, components laying in face-sharing contactwith each other may be referred to as in face-sharing contact. Asanother example, elements positioned apart from each other with only aspace there-between and no other components may be referred to as such,in at least one example. As yet another example, elements shownabove/below one another, at opposite sides to one another, or to theleft/right of one another may be referred to as such, relative to oneanother. Further, as shown in the figures, a topmost element or point ofelement may be referred to as a “top” of the component and a bottommostelement or point of the element may be referred to as a “bottom” of thecomponent, in at least one example. As used herein, top/bottom,upper/lower, above/below, may be relative to a vertical axis of thefigures and used to describe positioning of elements of the figuresrelative to one another. As such, elements shown above other elementsare positioned vertically above the other elements, in one example. Asyet another example, shapes of the elements depicted within the figuresmay be referred to as having those shapes (e.g., such as being circular,straight, planar, curved, rounded, chamfered, angled, or the like).Further, elements shown intersecting one another may be referred to asintersecting elements or intersecting one another, in at least oneexample. Further still, an element shown within another element or shownoutside of another element may be referred as such, in one example.

The disclosure also provides support for an inertial filter, comprising,a porous material, and an array of helical passages, each helicalpassage of the array of helical passages extending from a top surface ofthe porous material to a bottom surface of the porous material. In afirst example of the system, the array of helical passages comprises aplurality of helical passage units, each helical passage unit of theplurality of helical passage units including a central axis extendingfrom the top surface of the porous material to the bottom surface of theporous material. In a second example of the system, optionally includingthe first example, each helical passage unit of the plurality of helicalpassage units comprises at least one helical passage extending along thecentral axis, the at least one helical passage forming a helical pathabout the central axis from a first opening in the top surface of theporous material to a second opening in the bottom surface of the porousmaterial. In a third example of the system, optionally including one orboth of the first and second examples, each helical passage unit of theplurality of helical passage units comprises one helical passageextending along the central axis from the top surface of the porousmaterial to the bottom surface of the porous material. In a fourthexample of the system, optionally including one or more or each of thefirst through third examples, each helical passage unit of the pluralityof helical passage units comprises two helical passages extending alongthe central axis from the top surface of the porous material to thebottom surface of the porous material. In a fifth example of the system,optionally including one or more or each of the first through fourthexamples, each helical passage unit of the plurality of helical passageunits comprises three helical passages extending along the central axisfrom the top surface of the porous material to the bottom surface of theporous material. In a sixth example of the system, optionally includingone or more or each of the first through fifth examples, the porousmaterial is configured to absorb and/or retain and/or transport liquid,but generally not gas. In a seventh example of the system, optionallyincluding one or more or each of the first through sixth examples, thesystem further comprises: draining vias within the porous material. In aeighth example of the system, optionally including one or more or eachof the first through seventh examples, the porous material is comprisedof a plurality of laminated sheets of absorbent material. In a ninthexample of the system, optionally including one or more or each of thefirst through eighth examples, the porous material is comprised of asingle 3D printed monolith. In a tenth example of the system, optionallyincluding one or more or each of the first through ninth examples,helical passages within the helical passage unit comprise at least oneof overlapped helical passages, interwoven helical passages, righthanded tread helical passages, or left handed tread helical passages.

The disclosure also provides support for a method comprising: flowing agas, a liquid, and/or a solid through a planar inertial filter havinghelical passages within a porous material. In a first example of themethod, flowing the gas, the liquid, and/or the solid through the planarinertial filter having helical passages within the porous materialfurther comprises flowing the gas, the liquid, and/or the solid intoentrance holes of the helical passages, the entrance holes positioned ona top surface of the planar inertial filter. In a second example of themethod, optionally including the first example, flowing the gas, theliquid, and/or the solid through the planar inertial filter havinghelical passages within the porous material further comprises developingpartial annular flow as the gas, the liquid, and/or the solid travelsthrough a first section of the helical passages that is proximate to theentrance holes. In a third example of the method, optionally includingone or both of the first and second examples, flowing the gas, theliquid, and/or the solid through the planar inertial filter havinghelical passages within the porous material further comprises developingasymmetric annular flow as the gas, the liquid, and/or the solid travelsthrough a second section of the helical passages that is proximate tothe first section and farther from the entrance holes than the firstsection. In a fourth example of the method, optionally including one ormore or each of the first through third examples, flowing the gas, theliquid, and/or the solid through the planar inertial filter havinghelical passages within the porous material further comprises fullydeveloped annular flow as the gas, the liquid, and/or the solid travelsthrough a third section of the helical passages that is proximate to thesecond section and farther from the entrance holes than the secondsection. In a fifth example of the method, optionally including one ormore or each of the first through fourth examples, each of the helicalpassages comprises a tubular void having a boundary formed by the porousmaterial, and wherein flowing the gas, the liquid, and/or the solidthrough the planar inertial filter having helical passages within theporous material further comprises: impinging the liquid and/or the solidon the boundary of each of the helical passages, and wicking theimpinged liquid into the porous material away from the boundary of eachof the helical passages. In a sixth example of the method, optionallyincluding one or more or each of the first through fifth examples, theplanar inertial filter includes a drain connector, and wicking theimpinged liquid into the porous material includes channeling theimpinged liquid along one or more draining vias to the drain connector.In a seventh example of the method, optionally including one or more oreach of the first through sixth examples, the method further comprises:flowing the gas, and not the liquid and the solid, out of exit holes ofthe helical passages. In a eighth example of the method, optionallyincluding one or more or each of the first through seventh examples, theexit holes are positioned on a bottom surface of the planar inertialfilter that is directly opposite the top surface.

As used herein, the term “approximately” is construed to mean plus orminus five percent of the range unless otherwise specified.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. An inertial filter, comprising: a planarporous material; and an array of helical passages receiving at least amixture of at least gas and liquid, each helical passage of the array ofhelical passages extending from a top surface of the porous planarmaterial to a bottom surface of the porous planar material, the helicalpassages configured to passively induce centrifugal accelerations thatdrive liquid of the liquid/gas mixture to outer walls of the array ofhelical passages where droplets impinge onto the porous planar materialand are absorbed, and then are driven by wicking capillary forces awayfrom the helical passage walls.
 2. The inertial filter of claim 1,wherein the array of helical passages comprises a plurality of helicalpassage units, each helical passage unit of the plurality of helicalpassage units including a central axis extending from the top surface ofthe planar porous material to the bottom surface of the planar porousmaterial, wherein the planar porous material includes a plurality ofseparated draining vias extending along a length of the planar porousmaterial, and wherein the capillary forces drive the liquid to theplurality of draining vias, the filter further having a fluid outletcoupled with the plurality of draining vias to collect and drain liquid.3. The inertial filter of claim 1, wherein each helical passage unit ofa plurality of helical passage units comprises at least one helicalpassage extending along the central axis, the at least one helicalpassage forming a helical path about the central axis from a firstopening in the top surface of the porous planar material to a secondopening in the bottom surface of the porous planar material, wherein afilter pressure drop across the inertial filter remains constant untilthe planar porous material is fully saturated with liquid, and whereinat least portions of the separated draining vias are positioned parallelwith one another.
 4. The inertial filter of claim 3, wherein eachhelical passage unit of the plurality of helical passage units comprisesone helical passage extending along the central axis from the topsurface of the porous material to the bottom surface of the porousmaterial.
 5. The inertial filter of claim 3, wherein each helicalpassage unit of the plurality of helical passage units comprises threehelical passages extending along the central axis from the top surfaceof the porous material to the bottom surface of the porous material. 6.The inertial filter of claim 3, wherein helical passages within eachhelical passage unit comprises at least one of overlapped helicalpassages, interwoven helical passages, right handed thread helicalpassages, or left handed thread helical passages.
 7. The inertial filterof claim 1, wherein a cross-section parallel with the top surface of theporous planar material and the bottom surface of the porous planarmaterial of the a passage of the array of helical passages is a kidneyshaped hole.
 8. The inertial filter of claim 7, wherein the array ofhelical passages comprises a plurality of helical passage units, whereineach helical passage unit of the plurality of helical passage unitscomprises three helical passages, and wherein the cross-section of thethree helical passages is three non-touching kidney shaped holes havinga length greater than a pitch, the length being defined in thecross-section and representing a long dimension of the kidney shapedhole.
 9. The inertial filter of claim 1, wherein the porous planarmaterial is configured to absorb and/or retain and/or transport liquid,but generally not gas.
 10. The inertial filter of claim 1, wherein theporous material is comprised of a single 3D printed monolith.